Automatic grit feed

ABSTRACT

Lapidary apparatus for grinding rocks or stones into polished spheres, which are attractive works of art, comprising an automatic sphere grinder with automatic feeder, said apparatus including a grinding cup rotatable about a vertical axis and adapted to receive a work object to be ground into a sphere, a travelling boom, a pair of legs mounted on said boom and adapted to contact and rotate the work object, said legs contacting the work object on each side of the vertical axis of the cup to hold the work object in the cup, a motor crank arm connected to one end of the boom for reciprocably moving the boom and legs in a direction generally along the longitudinal axis of the boom so as to move the length of the legs over the work object to rotate it about a horizontal axis, a lift member mounted on the other end of the boom adapted to contact a stop member to momentarily lift the legs from the work object to allow the cup to spin the work object to another grinding position, a grit hopper having a feed port, a grit receiving member having an arcuate surface positioned below the feed port a distance such that when in normal position the arcuate surface receives a pile of grit having a positive angle of repose that shuts off the feed port, a shaft rotatably supporting the grit receiving member and having a handle extending downwardly therefrom of sufficient length to be heavy enough to support said arcuate surface in position beneath the feed port, a funnel mounted beneath the grit receiving member and over the work object, an actuating arm mounted on the boom and positioned so as to strike said handle to move the arcuate surface back and forth beneath the feed port to receive and dispense grit material into said funnel, and a water system with a water feed port positioned over the work object for feeding water thereto, said water feed port being positioned away from the funnel tube to prevent water from entering the funnel and clogging it with wet grit.

United States Patent [1 1 i Y Sharbaugh in] 3,828,979 Aug. 13, 1974AUTOMATIC GRIT FEED [76] Inventor: Joseph C. Sharbaugh, 164 Warrior Rd.,Drexel Hill, Pa. 19026 22 Filed: Sept. 5, 1972 [21] Appl. No.2 286,072

Related US. Application Data [62] Division of Ser. No. 143,799, May l7,1971, Pat. No.

[52] US. Cl. 222/129, 222/457 [51] Int. Cl. G01f 11/46 [58] Field ofSearch 222/145, 457, 556, 505,

[56] References Cited UNITED STATES PATENTS l2/l933 Swartz 222/457 X4/1956 Bello 222/500 X 4/1957 Whitlock 222/457 X PrimaryExaminer-Stanley H. Tollberg Attorney, Agent, or Firm-Smith, Harding,Earley & Follmer boom, a pair of legs mounted on said boom and adaptedto contact and rotate the work object, said legs contacting the workobject on each side of the vertical axis of the cup to hold the workobject in the cup, a motor crank arm connected to one end of the boomfor reciprocably moving the boom and legs in a direction generally alongthe longitudinal axis of the boom so as to move the length of the legsover the work object to rotate it about a horizontal axis, a lift membermounted on the other end of the boom adapted to contact a stop member tomomentarily lift the legs from the work object to allow the cup to spinthe work object to another grinding position, a grit hopper having afeed port, a grit receiving member having an arcuate surface positionedbelow the feed port a distance such that when in normal position thearcuate surface receives a pile of grit having a positive angle ofrepose that shuts off the feed port, a shaft rotatably supporting thegrit receiving member and having a handle extending downwardly therefromof sufficient length to be heavy enough to support said arcuate surfacein position beneath the feed port, a funnel mounted beneath the gritreceiving member and over the work object, an actuating arm mounted onthe boom and positioned so as to strike said handle to move the arcuatesurface back and forth beneath the feed port to receive and dispensegrit material into said funnel, and a water system with a water feedport positioned over the work object for feeding water thereto, saidwater feed port being positioned away from the funnel tube to preventwater from entering the funnel and clogging it with wet grit.

5 Claims, 9 Drawing Figures PMENIEB AUG 1 31974 SHEET 1 0F 2 swar WATERFIG. 2

FIG. 9.

AUTOMATIC GRIT FEED CROSS-REFERENCE TO RELATED APPLICATIONS Thisapplication is a division of my patent application Ser. No.l43,799,filed May 17, 1971 now US. Pat. No. 3,739,531.

BACKGROUND OF THE INVENTION This invention relates to lapidary equipmentand more particularly concerns a sphere grinder and automatic gritfeeder for grinding rocks or stones into polished spheres which arerecognized as attractive objects of art.

Lapidaries are people who cut, polish and engrave precious stones orrocks. Lapidaries may do this as a profession, or they may do this as ahobby and may join a lapidary society whose members enjoy working onstones and rocks.

It is believed that many more amateur lapidaries would be grinding rocksand stones into spheres if they did not think that sphere cutting wastoo difficult, too time consuming, and involved expensive equipment.

The simplest sphere grinder is a rotating cup. Loose grit is applied tothe cup and a rock is held in the cup by hand and slowly rotated so thatthe grit grinds the rock surface into a sphere. However, grinding asphere by hand involves constant attention and a great deal of timesince it calls for rotating the rock by hand against the spinning cupand feeding grit and water to the cup with a paint brush as needed. Sucha hand operation may take five to twenty-five hours, or more, before therock is ground into an acceptable sphere.

For a full description of the operation in hand grinding a sphere, Irefer to my article entitled Sphere Grinding In The Bargain Basementwhich appeared in the TUSCARORA BULLETIN, a publication of the TuscaroraLapidary Society, Inc., in the November and December, 1969 issues, sucharticle being hereby incorporated by reference.

Instead of grinding rock or stone into a sphere by this hand method, alapidary may use a machine. However, conventional machines may cost$100.00 to about $400.00. Also, such machines are fairly complicated andmay include a pair of facing cutter cups and shafts. Such sphere makermachines are made by Covington Engineering Corp., Redlands, Cal., and byHighland Park Mfg. Co., Inc., S. Pasadena, Cal., for example.

SUMMARY OF THE INVENTION It is an object of this invention to provide anautomatic sphere grinder including an automatic feeder, which apparatusis relatively simple and inexpensive.

The apparatus includes a rotatable grinding cup adapted to receive awork object such as a stone or rock to be ground into a sphere, atravelling boom, a pair of legs mounted on the boom for contacting androtating the work object, a motorized crank arm for reciprocably movingthe boom and contact legs in a direction generally along thelongitudinal axis of the boom, a stop member for contacting the end ofthe boom and lifting the legs away from the work object to allow therotating cup to spin the work object to another position, and automaticfeeder means for feeding a grinding material to the work object, saidfeeding means including a grit hopper having a grit feed port at thebottom for gravity feed therethrough, a grit receiving element mountedon a shaft and having a top surface positioned beneath said grit feedport for receiving a pile of grit and closing the feed port because ofthe angle of repose of the grit, a handle extending downwardly from saidreceiving element shaft and being heavier than the grit receivingelement to maintain the receiving element in upright normal position,and an actuating arm mounted on the boom and adapted to contact saidhandle during reciprocation of said boom to rotate said receivingelement shaft to move the receiving element and dump the grit from itstop surface onto the work object.

BRIEF DESCRIPTION OF THE DRAWINGS Objects and advantages of thisinvention, including its simplicity and economy, as well as the easewith which it may be adapted for use with existing equipment, willbecome apparent hereinafter and in the drawings, in which:

FIG. 1 is a view in side elevation of an automatic sphere grinder withautomatic feeder constructed in accordance with this invention, withparts being shown in section in order to better illustrate theinvention;

FIG. 2 is a view in top plan taken as indicated by the lines and arrows2-2 which appear in FIG. 1;

FIG. 3 is a partial view in side elevation, similar to FIG. 1, butshowing a later stage in operation with its lift lever resting on a stopmember so as to release its legs from contact with the work object;

FIG. 4 is a view in section taken as indicated by the lines and arrows4-4 which appear in FIG. 2;

FIG. 5 is a view similar to FIG. 4 but shows the stage of operation ofFIG. 3 whereas FIG. 4 shows the stage of operation of FIG. I;

FIG. 6 is an enlarged view of a portion of the automatic grit feedershowing how the grit forms a conical pile, because of the angle ofrepose of the grit, to shut off the grit feed port;

FIG. 7 is a view of a rough rock or stone which is to be ground into asphere;

FIG. 8 is a view of the rock after it has been sawed into a more or lesscube shape with the corners sawed off; and

FIG. 9 shows the rock in its final form after being ground and polishedinto a sphere by the apparatus of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Although specific terms are usedin the following description for clarity, these terms are intended torefer only to the structure shown in the drawings and are not intendedto define or limit the scope of the invention.

Turning now to the specific embodiment of the invention selected forillustration in the drawings, there is shown lapidary apparatus forgrinding rocks or stones into polished spheres comprising an automaticsphere grinder 11 which includes an automatic grit feeder l3. Spheregrinder 11 includes a rotatable grinding cup 15 which is mounted on avertical shaft 17 supported on table top 19 by support member 21. Shaft17 is driven by pulley 23, belt 25, and pulley 27 on drive shaft 29 ofcup motor 31 mounted on the bottom of table top 19.

Grinding cup is adapted to receive a rock or work object 33 to be groundinto a sphere.

A travelling boom 35 includes a central member 37 attached at one end totwo side members 39, and a lift lever 41 attached to side members 39 bybolt and wing nut 43 which permits lift lever 41 to be adjusted relativeto side members 39. Lift lever 41 is adapted to contact a stop member 45mounted on table top 19.

A motor 47 is supported on table top 19 by bracket 49. Motor crank arm51 is positioned in a hole 53 in the end of central member 37 of boom 35so as to reciprocate boom 35 in a direction substantially along the axisof the boom.

Extending outwardly from side members 39 are square mounting blocks 55which support circular mounting blocks 57 that contact legs 59 havingends inserted in radial holes in blocks 57. Legs 59 are provided withrubber tubes 61 for better contact with the surface of work object 33.bolts and wing nuts 63 connect blocks 55, 57 together, and the legs 59may be repositioned easily to accommodate different size rocks byturning back on wing nuts 63 to release the legs from mounting blocks57, rotating blocks 57, and retightening wing nuts 63.

Splash pan 65 is mounted on table top 19 around spinning cup 15 in orderto catch any splashing of the grinding mixture being used to grind workobject 33. A drain pipe 67 extends downwardly from splash pan 65 throughtable top 19.

Automatic grit feeder 13 includes a grit hopper 71 mounted above workobject 33 by horizontal support member 73 bracketed to slotted verticalsupport arm 74 which is connected to vertical support member 75 by boltand wing nut 76, with the bolt passing through a vertical slot insupport arm 74. Grit hopper 71 has a grit feed port 77 at its bottom forgravity feed of the grit therethrough.

A grit receiving element 79 is positioned beneath grit feed port 77 forreceiving a pile 81 of grit which closes feed port 77 because of theangle of repose of the grit. The pile 81 of grit forms a cone shape withthe apex of the cone at the grit feed port 77 and the sides of the conesloping downwardly and outwardly therefrom.

Grit receiving element 79, in the preferred form of the invention, ismade of wood and has the shape of a pie segment which is mounted on ashaft 33 extending through a grit funnel 85 suspended from horizontalsupport member 73 by straps 87. Grit receiving element 79 has an arcuatetop surface for receiving the grit, and shaft 83 has a handle 89extending downwardly therefrom which is of sufficient length so as to beheavy enough to support grit receiving element 79 in normal uprightposition beneath feed port 77.

Grit receiving element 79 is actuated to dump pile 81 of grit onto workobject 33 by an actuating arm 91 mounted on boom 35. Arm 91 contactshandle 89 during reciprocation of the boom to thereby rotate receiv-.ing element 79 about shaft 83 to dump the grit.

Funnel 85 is positioned around and beneath grit receiving element 79 andincludes a cone-shaped body 93 with a tube 95 extending downwardly fromthe cone apex and terminating in a funnel feed port 97 above work object33 and cup 15.

Automatic grit feeder 13 also includes a water reservoir 99 positionedabove funnel feed port 97, and a gravity feed water tube 101 extendingfrom water reservoir 99 to a position adjacent to but spaced away fromfunnel feed port 97 so that the water contacts the dumped grit after itpasses through the funnel feed port 97, thereby preventing waterentering funnel feed port 97 and clogging the funnel tube 95 with wetgrit. Water tube 101 is provided with a valve 103 in order to regulatethe flow of water.

In grinding a stone into a sphere by hand, the lapidary holds the stonein his hand and moves it against the edge of a rotating cup, adding agritting paste made of carborundum or silicon carbide and water betweenthe edges of the rotating cup and the stone. This work takes hours tocut a stone into a sphere.

In operation of the present invention, the stone or work object 33 isplaced in spinning cup 15 and is rotated about a horizontal axis by legs59 of boom 35 which, in the preferred embodiment of the invention, has anine inch stroke imparted to it by crank arm 51 of motor 47. When crankarm 51 reaches the horizontal position illustrated in FIG. 3, lift lever41 on boom 35 contacts stop member 45 which prevents further downwardmovement of lift lever 41 and lifts legs 59 away from the top of workobject 33, thereby allowing cup 15 to spin stone 33 to another position.As crank arm 51 continues in its travel, legs 59 return into contactposition on top of the newly positioned work object 33 and rotate thework object around a horizontal axis, thus moving the surface of workobject 33 into contact with the edges of spinning cup 15 and theabrasive grit which grinds the surface of the stone. In opera tion ofautomatic grit feeder 13, the grit in hopper 71 pours through feed port77 to form a pile 81 on the upper surface of grit receiving element 79.The pile 81 is in the form of a cone in accordance with the angle ofrepose of the grit, and when the pile grows big enough the cone of gritjams the exit port 77 to prevent more grit from passing therethrough.Accordingly, feed port 77 deposits a limited amount of grit on the topsurface of grit receiving element 79 which rotates with shaft 83 whenhandle 89 is actuated by actuating arm 91 of boom 35. As grit receivingelement 79 moves, the grit pours through feed port 77 to pour acontinuous band of grit on the upper surface of receiving element 79,and the grit is dumped off this upper surface as element 79 is moved ina reciprocable motion.

One of the advantages of the automatic grit feeder 13 is that it feedsabrasive material and yet the abrasive material does not wear out theparts of the grit feeder because there are so few moving parts. In otherwords, there is no wearing surface in contact with the abrasivematerial.

It has been found that 400 grit fine silica does not work in automaticgrit feeder 13 because it has a negative angle of repose and does notpour through grit feed port 77 which has a 1/32 inch diameter. However,200 grit silica and coarser grits work fine in automatic grit feeder 13.

Legs 59 are easily removable from mounting blocks 57 by turning back onthe wing nuts 63 and should be removed to clean the coarse grittherefrom before going on to a finer grit. Also, rubber tubes 61 shouldbe replaced so that each size grit has its own rubber tubes, therebyavoiding grit of different sizes being imbedded in the rubber andinterfering with the progressive fine grinding of the work object.

Legs 59 may be opened and closed to fit the size of the work object 33by rotating the position of mounting blocks 57 before clamping them inplace by turning down on wing nuts 63.

Also, grit feeder support arm 73 is movable vertically because it isfastened to a vertical arm 74 that is vertically slotted and may beraised and lowered and then clamped in place by bolt and wing nut 76.

l claim:

1. An automatic grit feeder comprising a grit hopper having a grit feedport at the bottom for gravity feed therethrough, means for closing saidgrit feed port automatically when a desired portion of said grit has fedthrough said feed port, said port closing means including grit receivingmeans positioned beneath said feed port for receiving said grit andforming a pile of grit thereon until the pile reaches such height thatit closes said feed port, means spacing said receiving means away fromsaid feed port a desired distance so as to form a pile of grit havingthe desired amount of grit, and means for actuating said grit receivingmeans to dump said pile of grit and open said grit feed port said gritreceiving means being exposed and including a grit receiving elementmounted on a shaft located below the grit feeding port.

2. The automatic grit feeder of claim 1 wherein said grit receivingmeans comprises a grit receiving element mounted on a shaft and having atop surface for receiving the grit, a handle extending downwardly fromsaid shaft, said handle being heavier than said grit receiving elementto maintain the receiving element in upright normal position, and saidactuating means is adapted to contact said handle to rotate saidreceiving element shaft to move the receiving element and dump the gritfrom its top surface.

3. The automatic grit feeder of claim 2 including means for feedingwater to mix with the dumped grit.

4. The automatic grit feeder of claim 2 including a funnel positionedaround the grit receiving element for funneling the dumped grit to adesired location, said funnel including a cone-shaped body with a tubeextending downwardly from the cone apex and terminating in a funnel feedport.

5. The automatic grit feeder of claim 4 including a water reservoirpositioned above the funnel feed port, and a gravity feed water tubeextending from the water reservoir to a position adjacent to but spacedaway from the funnel feed port so that the water contacts the dumpedgrit after it passes through the funnel feed port, thereby preventingwater entering the funnel feed port from clogging the funnel tube withwet grit

1. An automatic grit feeder comprising a grit hopper having a grit feedport at the bottom for gravity feed therethrough, means for closing saidgrit feed port automatically wHen a desired portion of said grit has fedthrough said feed port, said port closing means including grit receivingmeans positioned beneath said feed port for receiving said grit andforming a pile of grit thereon until the pile reaches such height thatit closes said feed port, means spacing said receiving means away fromsaid feed port a desired distance so as to form a pile of grit havingthe desired amount of grit, and means for actuating said grit receivingmeans to dump said pile of grit and open said grit feed port said gritreceiving means being exposed and including a grit receiving elementmounted on a shaft located below the grit feeding port.
 2. The automaticgrit feeder of claim 1 wherein said grit receiving means comprises agrit receiving element mounted on a shaft and having a top surface forreceiving the grit, a handle extending downwardly from said shaft, saidhandle being heavier than said grit receiving element to maintain thereceiving element in upright normal position, and said actuating meansis adapted to contact said handle to rotate said receiving element shaftto move the receiving element and dump the grit from its top surface. 3.The automatic grit feeder of claim 2 including means for feeding waterto mix with the dumped grit.
 4. The automatic grit feeder of claim 2including a funnel positioned around the grit receiving element forfunneling the dumped grit to a desired location, said funnel including acone-shaped body with a tube extending downwardly from the cone apex andterminating in a funnel feed port.
 5. The automatic grit feeder of claim4 including a water reservoir positioned above the funnel feed port, anda gravity feed water tube extending from the water reservoir to aposition adjacent to but spaced away from the funnel feed port so thatthe water contacts the dumped grit after it passes through the funnelfeed port, thereby preventing water entering the funnel feed port fromclogging the funnel tube with wet grit.